Question

What are some general properties of Arrhenius bases?

Short answer

Arrhenius bases increase OH⁻ concentration in water, raising the pH.

Step-by-step solution

Understanding Arrhenius Bases

The Arrhenius theory describes acids and bases in terms of their ability to dissociate in water. Specifically, an Arrhenius base is a substance that increases the concentration of hydroxide ions (OH⁻) in an aqueous solution.

Identifying Hydroxide Ions Producers

Arrhenius bases dissociate in water to produce hydroxide ions. A common example is sodium hydroxide (NaOH), which dissociates in water to form Na⁺ and OH⁻ ions.

Behavior in Water

When an Arrhenius base is dissolved in water, it releases its constituent ions. This process increases the pH of the solution due to the presence of OH⁻ ions, making the solution basic.

Examples of Arrhenius Bases

Typical examples of Arrhenius bases include substances like NaOH (sodium hydroxide), KOH (potassium hydroxide), and Ca(OH)₂ (calcium hydroxide). These compounds release hydroxide ions when dissolved in water.

Key concepts

Hydroxide Ions

Hydroxide ions, denoted as OH⁻, play a crucial role in determining the basicity of a solution. They are negatively charged ions comprised of one oxygen atom bonded to a hydrogen atom. When substances classified as bases release hydroxide ions into water, they form a solution that is higher in pH, reflecting a basic, or alkaline, environment. This contrasts with hydrogen ions (H⁺) released by acids, which make a solution acidic. Commonly, the presence of hydroxide ions in a solution is indicated by an increased pH value.

Dissociation in Water

Dissociation in water is an essential process for understanding how bases behave. When an Arrhenius base is introduced into water, it readily dissociates, or breaks apart, into its constituent ions. For example, sodium hydroxide (NaOH) dissociates into sodium ions (Na⁺) and hydroxide ions (OH⁻). This process is crucial because the dissociation of a base leads to the release of hydroxide ions, which directly affects the solution's pH. This is why Arrhenius bases are typically associated with increasing the solution's basicity.

Arrhenius Theory

The Arrhenius theory is a foundational concept in chemistry that provides a straightforward way to distinguish between acids and bases. According to this theory, acids are substances that increase the concentration of hydrogen ions (H⁺) when dissolved in water, whereas bases increase the concentration of hydroxide ions (OH⁻). This distinction is vital as it helps explain the chemical behavior of substances when dissolved in aqueous solutions. Most common household cleaning agents are based on this principle, where the release of hydroxide ions makes them effective in neutralizing acids and in various cleaning tasks.

pH Increase

The pH scale is a measurement system used to indicate the acidity or basicity of a solution, ranging from 0 to 14. When an Arrhenius base dissolves in water, it releases hydroxide ions, which increases the pH level of the solution. The more hydroxide ions present, the higher the pH, representing a more basic (or alkaline) environment. For example, a solution with a pH above 7 is considered basic. The pH scale itself is logarithmic, which means that each whole number change represents a tenfold change in acidity or basicity. Hence, a small increase in pH can significantly increase the solution's basicity.